Method for annealing domain wall displacement type magneto-optical disc and magneto-optical disc

ABSTRACT

A manufacturing method of a domain wall displacement type magneto-optical recording medium comprises the steps of depositing a magnetic layer on a substrate to prepare a disc, and irradiating the magnetic layer with a converged light beam while applying a magnetic field and annealing the magnetic layer a converged light beam between information tracks. A domain wall displacement type magneto-optical disc comprises a domain wall displacement layer in which a domain wall displaces, a memory layer that holds a recording magnetic domain according to information, a switching layer that is provided between the domain wall displacement layer and the memory layer and has a Curie temperature lower than that of those layers, and a disconnecting area that is provided in the domain wall displacement layer and disconnects a switching connection between information tracks, wherein the polarity of a residual magnetization at a boundary between the information track and the disconnection area is oriented in a certain direction.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a domain wall displacementreadout type magneto-optical disc and a manufacturing method thereofand, more in particular, to a method for annealing anneal tracks thatexist at both sides of an information recording track.

[0003] 2. Related Background Art

[0004] As a rewritable high density recording system, there is a systemavailable wherein, by using thermal energy of a semiconductor laser, amagnetic domain is written in a magnetic thin film to record informationand, by using a magneto-optical effect, this information is read.Further, in recent years, there has been an increasing demand forfurther increasing the recording density of the magneto-optical disc ofthis system so as to make it as a large-capacity recording medium. Bythe way, a line recording density of the magneto-optical disc and thelike largely depends on a laser wave length λ of a reproduction opticalsystem and a numerical aperture NA of an objective lens. In other words,when the laser wave length λ of the reproduction optical system and thenumerical aperture NA of the objective lens are decided, the diameter ofa beam waist is decided and, therefore, a spatial frequency at the timeof reproducing a recorded domain has a detectable limit only at about 2NA/λ.

[0005] Accordingly, in order to realize high density by the conventionalmagneto-optical disc, it is necessary to shorten the laser wave lengthof the reproduction optical system and enlarge the NA of the objectivelens. However, there is a limit to improvement of the laser wave lengthand the numerical aperture of the objective lens. For this reason, atechnology to think out a constitution of the recording medium and areading method and improve recording density is being developed.

[0006] For example, in Japanese Patent Application Laid-Open No.06-290496, the magneto-optical disc and its manufacturing method aredisclosed, the disc using a perpendicular magnetic anisotropymulti-layer film having at least s domain wall displacement layermagnetically linked, a switching layer and a memory layer.

[0007] This method uses an ingenious mechanism, wherein, at the time ofreproduction, a thermal gradient to be generated by irradiation of anoptical beam is used and the domain wall of a recorded mark of thedomain wall displacement layer is displaced without changing recordeddata in the memory layer, and the domain wall displacement layer ismagnetized so that a part of an optical beam spot area is uniformlymagnetized and a change of the polarization plane of the reflected lightof the optical beam is detected, thereby reproducing a recorded domainof the cycle below a diffraction limit.

[0008] By using this reproduction system, a reproduction signal becomesrectangular (FIG. 11D), and it is possible to reproduce the recordedmark of the cycle below the diffraction limit of a light withoutlowering the reproduction signal amplitude by depending on an opticalresolving power, and the magneto-optical disc capable of considerablyimproving the recording density and a transfer velocity becomespossible.

[0009] Note that, in this type of magneto-optical disc, in order toutilize the temperature gradient by irradiation of the light beam so asto easily cause the displacement of the domain wall of recorded mark ofthe domain wall displacement layer, a laser beam of high power isirradiated at the portion of adjacent two pieces of the anneal tracks(guide grooves) which make the information recording track of themagneto-optical disc exist between them, and a magnetic layer of theanneal track (guide groove) is annealed at high temperature andsubjected to an annealing process which degenerates a magnetic layer ofthe portion of the anneal track (guide groove). By this annealingprocess, a switched connection between the information recording tracksis disconnected and the domain wall is not formed along the side portionof the information domain track of the recorded mark. As a result, theaction of a domain wall coercivity is reduced, and more stabilizeddisplacement of the domain wall becomes possible. This annealing processcan obtain a good reproduction signal.

[0010] The reproducing action of the domain wall replacement typemagneto-optical disc will be described by using FIGS. 11A to 11D. Herewill be dealt with the constitutions of three layers: a memory layerwhich governs the storing of the recorded mark; the domain walldisplacement layer where the domain wall displaces and directlycontributes to the reproduction signal; and a switching layer whichswitches a link status between the memory layer and the domain walldisplacement layer.

[0011]FIG. 11A is a typical view which shows a magnetic domainreproducing state. A thick line 111 shows a domain wall of the domainwall displacement layer, and a narrow line 112 shows the domain wall ofthe memory layer only. FIG. 11B shows a state graph of a recording film,FIG. 11C a temperature state graph of a medium and FIG. 11D thereproduction signal. Note that the two pieces of the anneal tracks(guide grooves) which make the information recording track exist betweenthem, as described above, subjected to the annealing process where amagnetic layer is degenerated by irradiation of high powered laser beam.At the time of reproduction, the anneal track is heated until a Tstemperature condition (FIG. 11A) where the domain wall of the domainwall displacement layer of a domain wall displacement medium isdisplaced by irradiation of a light beam 116. Here, the Ts is the Curiepoint of the matter which constitutes the switching layer, and theswitching layer 22 (FIG. 11B) is in a link state with the memory layer21 and the domain wall displacement layer 23 by the switched connectionin a low temperature area. When the magneto-optical disc displaces inthe direction shown by an arrow mark 114 and is heated more than the Tstemperature by irradiation of the light beam, the link between thedomain wall displacement layer and the memory layer is put into adisconnected state (inside of a Ts constant temperature line shown bythe Ts of FIG. 11A. For this reason, as soon as the domain wall of therecorded mark arrives at this Ts temperature area, an effect of theannealing process (annealing process portion by laser is shown byreference numeral 113 in FIGS. 11A to 11D) of the two pieces of theanneal tracks (guide grooves) adjacent to the information recordingtrack also takes place, and the domain wall of the domain walldisplacement layer instantaneously displaces to the position where thedomain wall can stably exist energy-wise in relation to the temperaturegradient of the domain wall displacement layer, that is, to thedirection of an arrow mark 115 so that the domain wall can cross theinformation recording track at the highest temperature of the linedensity direction of the temperature rise by the light beam irradiation.In this way, a large portion of magnetic state of an area S which iscovered by the reproduction light beam becomes the same and, therefore,in the usual light beam reproduction principle, even if it is a minuterecorded mark which is not possible to reproduce, a reproduction signalnearly in a rectangular shape as shown in the drawing can be obtained.

SUMMARY OF THE INVENTION

[0012] The present invention provides a domain wall displacement typemagneto-optical disc where an error rate and a jitter of a reproductionsignal are improved, and a manufacturing method of the disc.

[0013] According to an aspect of the present invention, there isprovided a manufacturing method of a domain wall displacement typemagneto-optical recording medium comprising the steps of:

[0014] depositing a magnetic layer on a substrate to prepare a disc; and

[0015] irradiating the magnetic layer with a converged light beam whileapplying a magnetic field and annealing the magnetic layer a convergedlight beam between information tracks.

[0016] According to another aspect of the present invention, there isprovided a domain wall displacement type magneto-optical disccomprising:

[0017] a domain wall displacement layer in which a domain walldisplaces;

[0018] a memory layer that holds a recording magnetic domain accordingto information;

[0019] a switching layer that is provided between the domain walldisplacement layer and the memory layer and has a Curie temperaturelower than that of those layers; and

[0020] a disconnecting area that is provided in the domain walldisplacement layer and disconnects a switching connection betweeninformation tracks;

[0021] wherein the polarity of a residual magnetization at a boundarybetween the information track and the disconnection area is oriented ina certain direction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a view to explain a manufacturing method of the presentinvention;

[0023]FIG. 2 shows an annealing device to be used in the manufacturingmethod of the present invention;

[0024]FIGS. 3A, 3B, 3C and 3D show a timing chart to show the action ofa first embodiment of the present invention;

[0025]FIG. 4 shows an example of an application of an annealing magneticfield;

[0026]FIG. 5 shows another example of the application of the annealingmagnetic field;

[0027]FIG. 6 shows a jitter property graph of the first embodiment ofthe present invention;

[0028]FIG. 7 shows a pulse width fluctuation property graph by a secondembodiment of the present invention;

[0029]FIG. 8 shows another example of an annealing device to be used inthe manufacturing method of the present invention;

[0030]FIG. 9 shows a case where an annealing magnetic field parallel toa light beam scanning direction inside the disc surface is applied;

[0031]FIG. 10 shows a case where the annealing magnetic fieldperpendicular to the light beam scanning direction inside the discsurface is applied; and

[0032]FIGS. 11A, 11B, 11C and 11D are a view to explain the reproducingmethod of a domain wall displacement type magneto-optical recordingmedium.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033]FIG. 1 shows a schematic diagram to show a property of anannealing method of a magneto-optical disc of the present invention. Itshows a sectional view of a magneto-optical disc 3 at the stage where astep of laying on a magneto-optical disc substrate 1 comprising glass orplastic as a material a magnetic layer 2 which includes at least adomain wall displacement layer where the domain wall displaces, a memorylayer which holds information as a recording magnetic domain and aswitching layer provided between the domain wall displacement layer andthe memory layer and having Curie temperature lower than those layershas been completed. While any protective layer is still not formed atthe stage of FIG. 1, it does not matter whether the protective layerexists when annealing the disc. Here, a character d denotes one of theinformation recording tracks, and the information track is an area whichforms a recording magnetic domain to hold the information such as a userdata etc. In general, this convex portion provided on the substrate isreferred to as a land. Magneto-optical disc of FIG. 1 has a constitutionin which the light beam for use of forming an anneal track enters fromthe back side of the substrate where the magnetic layer 2 is not formed.Characters a and a′ which make an information recording track d existbetween them denote anneal tracks, which are formed by a laser annealingwith a higher light intensity than that at writing an information on theinformation recording track d.

[0034] In the present drawing, the anneal tracks a and a′ serve also asthe guide grooves to control the light beam at the center of theinformation recording track d in the reproduction step. In general, theconcave portion provided on the substrate is referred to as a groove.

[0035] In the present embodiment, the lands (convex portions) on thesubstrate 1 are taken as information recording tracks and the grooves(concave portions) as the anneal tracks, but the constitution of themagneto-optical disc is not limited to this. For example, a constitutionwherein the lands (convex portions) are taken as the anneal tracks andthe grooves (concaves) are taken as the information recording tracks isalso allowable.

[0036] The laser spots denoted by characters b and b′ show the convergedlight beams when annealing anneal tracks a and a′, which enter from theback of the substrate.

[0037] In the drawing, the laser spots of b and b′ are illustrated as ifthe two points were irradiated at the same time. This is to clarify thatthe directions of annealing magnetic fields applied to the two annealtracks which are adjacent to the information recording track aredifferent.

[0038] Characters c and c′ show the polarities of applied magneticfields in the case where the anneal tracks a and a′ are annealed. In thepresent embodiment, the direction of the applied magnetic field is fromone side of the substrate on which the magnetic layer 2 is provided tothe other side of the substrate (i.e., the back side of the substrate)when anneal track a is annealed, and the direction of the appliedmagnetic field is from the back side of the substrate to the side onwhich the magnetic layer 2 is provided when anneal track a′ is annealed.In addition, the annealing magnetic fields at the adjacent anneal trackswith the information recording track d made to exist between them haveopposed polarities.

[0039] In order to form the anneal tracks by applying thus annealingmagnetic fields perpendicular to the substrate surface, a device asshown in FIG. 2 is suitable.

[0040] A magneto-optical disc 100, wherein a magnetic layer 2 is formedon a magneto-optical disc substrate 1 made of glass or plastic andfurther a protective layer 3 is formed, is held on a spindle motor witha magnetic chucking and the like, and is constituted such that it isrotatable against an axis of rotation.

[0041] A laser light for forming the anneal track generated from asemiconductor laser light source 7 is changed to a parallel ray by acollimator lens 8 and passes through a beam splitter 9 and is convergedby a condenser lens 6. Then a predetermined position of themagneto-optical disc 100 is irradiated with the converged laser light asa beam from the back. Note that the condenser lens 6 is driven by adrive actuator 5.

[0042] On this occasion, the condenser lens 6 is constituted such thatit is controlled by actuator 5 to move in a focusing direction and atracking direction so that the laser light successively places a focuson the magnetic layer 2. The condenser lens 6 also moves along the guidegroove engraved on the magneto-optical disc.

[0043] On the other hand, the reflected light which reflected from thesurface of magneto-optical disc surface passes through a route inreverse to the incident light and arrives at the beam splitter 11 and isreflected at a right angle and passes through a λ/2 plate 10. This λ/2plate is a filter to rotate a the reflected light at 90° in thepolarizing direction of the incident light.

[0044] Further, the reflected light enters the polarized beam splitter11 and is put into two condenser lenses 12 by the polarity of themagneto-optical disc magnetization of the magneto-optical disc 100. Twopieces of photo sensors 13 detect the intensities of the incident lightswhich enter the sensors respectively. The detected resultants areamplified respectively by a differential amplification circuit 14 whichdifferentially amplifies the signal converged and detected respectivelyaccording to the polarization direction and by a summing amplificationcircuit 15 which summing-amplifies the signal converged and detectedrespectively according to the polarization direction. A light magneticsignal and by a summing signal from the differential amplificationcircuit 14 and the summing amplification circuit 15 are synthesized andbinarized by a digital circuit 200 and outputted to a controller 17. Inaddition, the number of rotations of the magneto-optical disc, anannealing radius, an annealing sector information and so forth areinputted to controller 17, and a signal to control an annealing power isoutputted to a LD driver 16. The LD driver 16 irradiates a laser to asubstrate 1 under a predetermined condition according to that signal.

[0045] Further, the controller also controls a magnetic head driver 19at the same time, and outputs a signal which controls the polarity ofthe annealing magnetization and the like.

[0046] Reference numeral 18 denotes a magnetic head to apply a magneticfield to a laser-irradiated portion of magneto-optical disc 1 whenforming an anneal track, and sandwiches the magneto-optical disc 100 andis arranged in a manner that opposes to condenser lens 6. Magnetic head18 is used to record information and to reproduce it. In the annealing,a semiconductor laser 7 irradiates the LD driver 16 with an anneal laserpower and, at the same time, the magnetic head 18 is allowed to generatea perpendicular magnetic field of a polarity corresponding to a polaritysignal of a magnetic field applied for annealing an anneal track(hereinafter referred to as “annealing applied magnetic field”) bymagnetic head driver 19. The magnetic head 18 is constituted such that,coupled with an optical head, it moves in the radial direction of themagneto-optical disc 1 and, at the annealing step, applies a magneticfield successively to the laser-irradiated portion of themagneto-optical disc 3 to perform a desired annealing.

[0047] However, means which reproduces the information from thereflected light from the magneto-optical disc is not necessarilyrequired. Such a means is utilized as means to detect a pre-format andthe like and to reproduce a magneto-optical signal when controlling atiming to switch the polarity of the annealing applied magnetic field bythe reflected light from the magneto-optical disc, or when checkingwhether a desired property develops in the information recording trackor not after the annealing of the anneal track. In the case, aconstruction where a parameter such as a laser power according to theannealing, an applied magnetic field or the like is changed into a valuerelative to the recording or reproduction by the controller 17 isrequired.

[0048] In the idea of the above described annealing method and theannealing means, the action of annealing the anneal track will bedescribed by using FIGS. 3A to 3D. FIG. 3A shows an annealing powerON/OFF signal which shows the start of the annealing, FIG. 3B shows anapplied magnetic field polarity change timing signal which shows atiming to change the polarity of the applied magnetic field, FIG. 3Cshows an applied magnetic field polarity control signal which controller17 outputs to magnetic head driver 19, and FIG. 3D shows a generatedmagnetic field of magnetic head 18. An irradiating power of the laser isset to a desired annealing power by an annealing start command fromcontroller 17. Although the annealing power is different depending on aproperty of the magneto-optical disc, but it is typically about twotimes that of the recording power. At the same time of the irradiationof the laser power, the annealing magnetic field is applied by themagnetic head 18. On this occasion, the polarity of the appliedannealing magnetic field is allowed to generate the magnetic field ofthe polarity corresponding to a polarity of the applied magnetic fieldcontrol signal from the controller 17. As described below, the absolutevalue of the magnetic field intensity is preferable to be larger thanabout 50 Oe. In order to execute the property of the present invention,it is necessary to switch the polarity of the applied magnetic field atleast more than one time for one cycle, and this switching timing iscontrolled by an applied magnetic field polarity change timing signalfrom the controller 17. The applied magnetic field polarity changetiming signal can be formed by counting a clock for rotation control ofthe spindle and can be also formed by detecting the reflected light suchas a phase pit which causes a change of reflectivity embedded in advancein the anneal track of the magneto-optical disc as an applied magneticfield change timing. The later makes it possible to control themagneto-optical disc by higher position accuracy.

[0049] Since the switched portion of the polarity of the annealingapplied magnetic field is considered to have adverse effect on theinformation recording track, the area where the polarity of theannealing applied magnetic field is switched is preferably the areawhere the adjacent information recording track is not an user data area,for example, preferably a header area which shows a sector positioninformation and the like. Further, an applied magnetic field polarityswitching area may be specially provided. By these means and processes,it is possible to control the applied magnetic field to a predeterminedmagnitude and polarity in annealing the anneal tracks adjacent to bothsides of the information recording track.

[0050] Examples of the applied magnetic field polarity change timing ina case where the magneto-optical disc is annealed by these means areshown in FIGS. 4 and 5. In FIGS. 4 and 5, reference numeral 41 denotesthe anneal track, and reference numeral 42 denotes the informationrecording track. Among the anneal tracks, the hatching portion shown byT has the applied magnetic field at the time of annealing in the upwarddirection to the plane of the drawing, and among the anneal tracks, thehatching portion shown by F has the applied magnetic field at the timeof annealing in the downward direction to the plane of the drawing. InFIG. 4, switching of the polarity of the annealing magnetic field isperformed only when the magnetic field-applying means moves to the nextanneal track and the switching is one time for one cycle of the annealtrack. In contrast to this, in FIG. 5, since the anneal track of onecycle is divided into four continuous magnetic areas, the switching ofthe polarity of the applied magnetic field is performed five times. Thewhite portion 42 indicates the information recording track in FIG. 5.The figure shows that the polarities of the annealing magnetic fields inadjacent portions T and F of the recording tracks are reversed.

[0051] The timing of switching the applied magnetic field is not limitedto the above. The gist of the switching is adaptable not only to CAV butalso to format, of zone CAV, CLV and zone CLV, assuming that the appliedmagnetic fields at the time of annealing anneal tracks adjacent to bothsides of an information track have opposite polarities.

[0052] (Embodiment 1)

[0053] The present invention was executed by the device described inFIG. 2. The device of FIG. 2 applies an annealing magnetic fieldperpendicular to the magneto-optical disc surface.

[0054]FIGS. 6 and 7 show properties in embodiments of the presentinvention and the comparative examples, as explained below.

[0055] After completing the formation of the magnetic layer, theannealing of the anneal track was conducted by laser beam under variousconditions.

[0056] In FIG. 6, the ordinate shows a jitter property. The jitterproperty is better as the value of the jitter property is smaller. Theabscissas of FIG. 6 shows applying methods of the magnetic field at thetime of annealing the anneal track.

[0057] Described in order from the left side on the axis of the abscissaare the methods

[0058] (1) wherein, as comparative example 1, the applied magneticfields at both of the anneal tracks adjacent to the informationrecording track were taken as −300 Oe and were applied to all the annealtracks the annealing magnetic field of the same polarity at the samemagnitude.

[0059] (2) wherein, as comparative example 2, the applied magneticfields at both of the anneal tracks adjacent to the informationrecording track were taken as+300 Oe, which was the same as (1) inannealing magnetic field.

[0060] (3) wherein, as comparative example 3, the applied magneticfields at both of the anneal tracks adjacent to the informationrecording track were taken as 0 Oe, and the annealing magnetic field wasnot applied at the time of forming the anneal track.

[0061] (4) wherein, as example 1, the applied magnetic fields at both ofthe anneal tracks adjacent to the information recording track wereinversed in polarity by one cycle interval, and the generated magneticfield was taken as ±300 Oe, which corresponds to FIG. 4.

[0062]FIG. 7 is the same as FIG. 6 in axis of abscissas, and the axis ofordinates shows a aberration amount of the reproduction signal pulsewidth in relation to the regular pulse width in the reproduction signal.If the pulse width is near to “0”, it shows that it is near to thedesired pulse width.

[0063] Table 1 shows annealing magnetic field applied conditions andreproduction properties. TABLE 1 Table 1: Annealing magnetic field(magnetic field applied in the direction perpendicular to the discsurface) and reproduction property. Comparative Comparative ComparativeExample 1 Example 2 Example 3 Example 1 Condition Annealing availableavailable not available available of Magnetization Annealing AppliedMagnetization Reversal of not available not available not availableavailable Applying Polarity Intensity of +300 −300 0 ±300 AnnealingMagnetization Length of one cycle one cycle — one cycle ContinuousMagnetization Area Reproduction Jitter good good bad good PropertyProperty Estimation Pulse Width bad Bad a little good Property badEstimation Overall bad bad bad very good Estimation

[0064] Regarding jitter property, example 1 shows that a jitter value islow. (FIG. 6, Table 1)

[0065] The pulse widths regarding the three types of the method forapplying the annealing magnetic field were estimated. Comparativeexamples 1 and 2 have large aberrations in the reproduction signal pulsewidth (FIG. 7, Table 1). Embodiment 1 has the most excellent performanceamong the four experiments even in pulse width.

[0066] From the result of these experiments, it is evident that, in thecase where the applied magnetic fields at both of the anneal tracksadjacent to the information recording track are inversed at intervals ofevery one cycle and the generated magnetic field is taken as ±300 Oe,the jitter property is excellent and the pulse width fluctuation is notgenerated, and it is the most suitable annealing condition among theabove described conditions.

[0067] In this way, the remanent magnetization at the boundary betweenthe anneal track, where, though there is a deterioration of the magneticproperty due to the laser annealing of the present invention, themagnetic property is not lost completely, and the information recordingtrack is taken as a predetermined polarity by both of the adjacentanneal tracks which make the information recording track exist betweenthem, so that the influence for the magnetic recording track in theinformation recording track is offset and the influence can beequalized. In this way, it is possible to provide the magneto-opticaldisc, which can obtain the reproduction signal of high quality, andfurther improve the recording density.

[0068] The remanent magnetization at the time of the above describedannealing has been confirmed not to be inversed by a recording powerusually used and a recording magnetic field usually used.

[0069] (Embodiment 2)

[0070] In FIG. 8 is shown a schematic diagram to show a property of thesecond embodiment of the annealing method of a magneto-optical disc ofthe present invention. In the drawing, what is different from embodiment1 is that a ring head is used, where the magnetic disc 18, which appliesthe magnetic field at the time of annealing, can apply the annealingmagnetic field in the in-plane direction of the face of the disc to aheated area on the recording medium. In this way, the magnetic fieldwhich is parallel to the magneto-optical disc surface can be applied toa heated annealing portion. In the case where the magnetic field isapplied to the inside of the magneto-optical disc surface, there existtwo directions parallel and perpendicular to the scanning direction ofthe light beam. In FIG. 9, an example of the annealing applied magneticfield was shown, where the annealing applied magnetic field is in thein-plane direction to the face of the magneto-optical disc and parallelto the light beam scanning direction. In the case where the annealingmagnetic field is applied in this direction, it is not necessary toconsider the polarity of the magnetic field and it does not matterwhether it is the same polarity or different. In FIG. 10, an example ofthe annealing applied magnetic field, where the annealing magnetic fieldis perpendicular in the plane of the face of magneto-optical disc, isshown. In the case of FIG. 10, when the annealing magnetic field of thereverse polarity is applied, it is necessary to certainly apply theannealing magnetic field of the same polarity since there is a risk ofthe magnetic field line loop of the remanent magnetization owned by theadjacent anneal tracks being multiplied on the information recordingtrack.

[0071] As shown in FIGS. 9 and 10, in order to change the polarity ofthe generated magnetic field to the scanning direction of the lightbeam, the direction of the ring head of FIG. 8 may be changed 90°. Asalready described as above, in FIG. 10, although the annealing appliedmagnetic fields have the same polarity, the polarity of the appliedmagnetic field does not cause any specific problem in the case where theannealing applied magnetic fields are parallel to the light beamscanning direction. Further, in the present embodiment, though the ringhead was used in order to generate the magnetic field parallel to themagneto-optical disc surface, there is no limit to this, but it does notmatter specifically whatever shape it has, provided the magnetic fieldparallel to the magneto-optical disc surface can be applied to the laserirradiated portion at the time of annealing.

[0072] In this way, the remanent magnetization at the boundary betweenthe anneal track, where, though there is a deterioration of the magneticproperty due to the laser annealing of the present invention, themagnetic property is not lost completely, and the information recordingtrack is directed to the direction of the inside of the magneto-opticaldisc surface, so that the influence can be reduced for the magnetic areaof the perpendicular direction recorded in the information recordingtrack, and it is further possible to equalize the influence.

[0073] Note that the remanent magnetization at the time of the abovedescribed annealing is confirmed not to be inversed by the usually usedrecording power and the recording magnetic field.

[0074] As described above, the remanent magnetization at the boundarybetween the anneal track, where, though there is a deterioration of themagnetic property due to the laser annealing of the present invention,the magnetic property is not lost completely, and the informationrecording track is equalized and the influence of the remanentmagnetization is taken as a predetermined polarity by both of the annealtracks which make the information recording tracks exist between them,so that a bad influence on the information recording track can beoffset, and the jitter property and the pulse width fluctuation can beimproved. Further, the remanent magnetization at the boundary betweenthe anneal track and the information recording track is directed to thedirection of the inside of the magneto-optical disc surface, so that theinfluence for the magnetic area in the perpendicular direction recordedin the information recording track can be equalized. In this way, thereproduction signal having higher quality than that of the conventionalmethod can be obtained. Furthermore, since the information recordingtrack width can be made narrower than that of the conventional method,it is possible to further improve the recording density of themagneto-optical disc.

What is claimed is:
 1. A manufacturing method of a domain walldisplacement type magneto-optical recording medium comprising the stepsof: depositing a magnetic layer on a substrate to prepare a disc; andirradiating the magnetic layer with a converged light beam whileapplying a magnetic field and annealing the magnetic layer a convergedlight beam between information tracks.
 2. The manufacturing methodaccording to claim 1, wherein said magnetic field is parallel to thedirection of a scanning with said light beam in the surface of saiddisc.
 3. The manufacturing method according to claim 2, wherein saidmagnetic fields have the same magnitude and different polarity betweenthose applied to their respective information tracks adjacent to eachother.
 4. The manufacturing method according to claim 2, wherein saidmagnetic fields have the same magnitude and same polarity between theirrespective information tracks adjacent to each other.
 5. Themanufacturing method according to claim 1, wherein said magnetic fieldsare perpendicular to the disc surface and have the same magnitude anddifferent polarity between those applied to their respective informationtracks adjacent to each other.
 6. The manufacturing method according toclaim 1, wherein said magnetic fields are perpendicular to the directionof a scanning with said light beam in the surface of the disc, and havethe same magnitude and same polarity between those applied to theirrespective information tracks adjacent to each other.
 7. Themanufacturing method according to claim 1, wherein an intensity of saidmagnetic field is not less than 50 Oe.
 8. The manufacturing methodaccording to claim 1, wherein said magnetic fields have its polarityswitched every one cycle of the disc.
 9. The manufacturing methodaccording to claim 1, wherein said magnetic fields have its polarityswitched several times in one cycle of the disc.
 10. The manufacturingmethod according to claim 9, wherein the area where the polarity isswitched is an area other than a user data area.
 11. A domain walldisplacement type magneto-optical disc comprising: a domain walldisplacement layer in which a domain wall displaces; a memory layer thatholds a recording magnetic domain according to information; a switchinglayer that is provided between the domain wall displacement layer andthe memory layer and has a Curie temperature lower than that of thoselayers; and a disconnecting area that is provided in the domain walldisplacement layer and disconnects a switching connection betweeninformation tracks; wherein the polarity of a residual magnetization ata boundary between the information track and the disconnection area isoriented in a certain direction.
 12. The domain wall displacement typemagneto-optical disc according to claim 11, wherein the direction ofsaid residual magnetization is switched in polarity at a predeterminedcycle.
 13. The domain wall displacement type magneto-optical discaccording to claim 12, wherein said switching occurs one cycle of thedisc as an unit.